Cut-off device for concrete structures

ABSTRACT

A cut-off element for concrete structures is formed by a plastic material flask having a flat-closed base and a tapering side envelope forming an acute angle with the base, said angle being between 25° and 60° for generating expansion forces so as to provoke a fracture of the concrete part along the cut-off zone defined by the base, and a lifting movement with slight amplitude of the concrete block after cut-off.

BACKGROUND OF THE INVENTION

The invention relates to a device for cut-off or demolition of aconcrete part, comprising means for inserting at least one cut-offelement equipped with an elemental recipient designed to receive areactive agent of chemical or mechanical nature to cause cracking of theconcrete part by expansion effect.

START OF THE ART

A cut-off device using reentrant means placed in position before theconcrete casting operation is performed to create a series of channelsin the mass of hardened concrete has already been proposed. The reactiveagent is then inserted in the channels communicating with the differentrecipients. Implementation of such a reentrant process makes use of aremovable cage having a plurality of vertical rigid bars. The reactionof the expansion agent causes an explosion of the concrete mass, whichrequires the exploded concrete blocks to be dismantled.

OBJECT OF THE INVENTION

The object of the invention is to achieve a cut-off or demolition deviceof simple construction enabling the breaking zone of the part of aconcrete structure to be demolished to be defined precisely, withoutaffecting the mechanical strength of the rest of the structure.

The device according to the invention is characterized in that therecipient of each cut-off element is formed by a flask, made inparticular of plastic material, having a flat closed base, and a lateralcasing forming an acute angle with the base, said angle being comprisedbetween 25° and 60° to generate expansion forces designed to causefracturing of the concrete part along the breaking zone defined by thebase, and a lifting movement of small amplitude of the concrete blockafter cut-off. The apex of the casing is fixed to a support means forplacing the base at the required demolition level.

According to a preferred embodiment, the support means comprise a rigidtube joined to a tubular connecting spout arranged at the apex of thecasing, said tube acting as inlet channel for insertion of thedemolition agent into the flask.

Insertion of each cut-off element can be performed individually, orgrouped by means of a positioning frame, before or after the concretecasting operation.

According to one feature of the invention, the positioning frame isfixed before the concrete casting operation to salient reinforcing barsby means of spacers spaced angularly between the different tubes of thecut-off elements. The spacers advantageously extend in the radialdirection towards the inside of the positioning frame to confine anorifice for axial passage of the concrete casting pipe.

The flat base of the flask of each cut-off element is generally arrangedhorizontally and extending perpendicularly to the direction ofinsertion. This results in a horizontal fracture of the concrete along aplane passing through all the coplanar bases of the flasks. The blockcut-off at the base then simply has to be lifted and the operation isfinished.

It is also possible to obtain a diagonal fracture by using flasks withoblique bases arranged on the positioning frame in an inclined plane.

According to a development of the invention, each flask can be filledwith a delayed-action expansive agent and is then placed in positionbefore or after the concrete is cast, without making use of the fillingtubes.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from thefollowing description of an embodiment of the invention given as anon-restrictive example only and illustrated in the accompanyingdrawings in which:

FIG. 1 is a schematic cross-sectional view of a cut-off elementaccording to the invention;

FIG. 2 represents the flask of the cut-off element of FIG. 1 associatedto a guiding means facilitating penetration into the concrete;

FIG. 3 shows an elevation of the positioning frame equipped with severalcut-off elements for placing in position before the concrete is cast;

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is a view of a flask adapted for filling with a delayed-actionreactive agent;

FIG. 6 shows a device for fixing a tube onto a support jig;

FIG. 7 represents an alternative embodiment of FIG. 6; and

FIG. 8 is a schematic cross-sectional view of another embodiment of acut-off element according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIG. 1, a cut-off element 10 for a concrete structuredemolition device comprises a flask 12, preferably made of plasticmaterial, designed to be joined to a support part 14 formed by avertical tube 16. The flask 12 is in the shape of a hollow pocket withan appreciably flat closed base 18 joined to a tapered lateral casing20. It is clear that any other revolution shape can be used to achievethe casing 20.

The base 18 can also be convex to compensate the pressure generated bythe concrete when casting takes place.

The casing 20 forms an acute angle with the base 18, said angle with thebase being preferably comprised between 25° and 60°. A tubular spout 22is arranged at the top of the casing 20 to receive the bottom end of thetube 16. Fixing of the tube 16 to the casing 20 is performed by screwingor by any assembly means.

According to a first operating mode, the cut-off element 10 is insertedvertically in the fresh concrete 24 after the concrete casting operationhas been performed. The length of the tube 16 is chosen such that thetop end protrudes out and acts as access orifice 26 for insertion of adestruction agent, for example of the chemical or mechanical expansivetype.

The depth of penetration of the cut-off element 10 into the concrete 24determines the breaking zone 28 precisely. After the demolition agenthas been inserted, an expansion effect occurs inside the plastic flask12 after a certain time. The resulting reaction forces F are distributedperpendicularly along the wall of the tapered casing 20 and generateradial components F1 extending parallel to the base 18 and verticalcomponents F2 perpendicular to the base 18. This results in horizontalfracturing of the concrete in the plane passing through the flat base 18of the flask 12, which determines the cut-off zone 28. The action of thevertical components F2 causes a slight lifting movement of the concreteblock when cut-off is performed.

According to FIG. 2, insertion of the cut-off element 10 into the freshconcrete is facilitated by a guiding means 30 fixed to the external faceof the flat base 18. The guiding means 30 is formed by a cone, made forexample of concrete, the apex whereof is facing downwards and the basewhereof is in contact with the base 18.

Depending on the cross-section of the concrete structure to be cut-off,a plurality of cut-off elements 10 are placed in position in the freshconcrete. Insertion of these elements can be performed individually, orgrouped on a common positioning frame 32. Insertion by means of apositioning frame enables simultaneous and quick penetration of the setof flasks 12 into the fresh concrete. The demolition agent is theninserted in the flasks 12 via the orifices 26 of the different tubes 16.After the expansion reaction of the demolition agent, horizontalfracturing of the concrete enables cut-off to be achieved by a simplevertical lifting of the fractured concrete block.

According to the alternative embodiment of FIGS. 3 and 4, thepositioning frame 32 equipped with the different cut-off elements 10 isplaced in position before the concrete 24 is cast. The positioning frame32 is fixed beforehand to the reinforcing bars 34 salient to receive thepile by spacers 36 spaced angularly between the tubes 16 and resting ona hoop 39 securedly fixed to the reinforcing bars.

The reinforcing bars 34 are formed by steel concrete bars surroundingthe tubes 16 coaxially, and the spacers 36 extend radially towards theinside of the positioning frame 32 to define the internal orifice 38 forpassage of the concrete casting pipe (not represented). All the bases 18of the flasks 12 are arranged appreciably in the same horizontal plane.

In the two cases of placing the cut-off elements 10 in position after orbefore the concrete is cast, the expansive agent inlet tubes 16 remainintegrated in the concrete block recovered after cut-off.

The flat base 18 of the flasks 12 enables a horizontal fracture of theconcrete block to be obtained according to the cut-off zone 28. It isclear that a diagonal fracture can be obtained by means of flasks havingbases inclined at a preset angle corresponding to the breaking plane, asshown in figure 8.

According to another alternative embodiment, the flasks 12 are notextended by tubes 12 but are filled directly with a delayed-actionexpansive agent of chemical or mechanical nature. In FIG. 5, each flask112 comprises for this purpose a base 118 formed by a removable cover,which cover is closed after filling with the delayed-action expansiveagent. In this case, the spout 122 is sealed off and the conical ortapered shape of the casing 120 is similar to that of FIG. 1.

The flasks 112 filled with the delayed-action expansive agent are eitherplaced in position before the concrete is cast by means of a supportframe or placed in position in the fresh concrete after casting by meansof a recoverable rod.

The delayed-action expansion effect can have a specific time delay,preferably more than 2 days, depending on the size of the structure, thenature of the concrete and the ambient temperature.

The plastic material of the flasks 12, 112 can be replaced by any otherequivalent breakable or deformable material, for example glass.

In FIG. 6, a device 200 for fixing a tube 16 onto a support jig 202comprises a securing clamp 203 associated to a profiled support part 204wherein a tube 16 is engaged. The profiled support part 204 has twoflexible branches designed to move towards or away from one anotherdepending on whether the clamp 203 is in the closed or open position.

After the concrete has been cast, the support jig 202 equipped with aplurality of tubes 16 and flasks 12 is placed on the hoop 39. The clamp203 is actuated to the slackened position and each tube 16 is descendedindividually to the bottom. At the end of travel, the clamp 203 isclosed to secure the tube 16.

After the cut-off operation has been performed, all the clamps 203 areopened and the support jig 202 can thus be re-used on the work-site forcutting-off another pile of the same dimension.

With reference to FIG. 7, the device 300 for fixing the tube 16 isformed by an elastically deformable clipping part 302 of appreciablycircular cross-section.

What is claimed is:
 1. A device for cut-off of a concrete part,comprising: means for inserting at least one cut-off element equippedwith an elemental recipient designed to receive a demolition agent ofchemical or mechanical nature to cause cracking of the concrete part byexpansion effect, wherein the recipient of each cut-off element isformed by a flask, made in particular of plastic material, having aclosed base, and a lateral casing forming an acute angle with the base,said angle being between 25° and 60° to generate expansion forcessubstantially in a horizontal and upwardly direction for fracturing ofthe concrete part along a breaking zone defined by the base of saidflask, and a lifting movement of small amplitude of the concrete partafter cut-off.
 2. The device for cut-off of a concrete part according toclaim 1, wherein the apex of the casing is fixed to a support means forinserting the base down to the breaking zone.
 3. The device for cut-offof a concrete part according to claim 2, wherein the support means of acut-off element comprise a rigid tube joined to a tubular connectingspout arranged at the apex of the casing, said tube acting as inletchannel for insertion of the demolition agent into the flask.
 4. Thedevice for cut-off of a concrete part according to claim 3, wherein eachtube is assembled on a support jig by means of a fixing devicecomprising a securing clamp or a clipping part.
 5. The device forcut-off of a concrete part according to claim 1, wherein the base of theflask is associated with a guiding means to facilitate penetration ofthe cut-off element into the concrete part before being cast.
 6. Thedevice for cut-off of a concrete part according to claim 1, wherein theflat base of the flask of each cut-off element is arranged horizontallyand extends perpendicularly to the direction of insertion.
 7. The devicefor cut-off of a concrete part according to claim 1, wherein the flatbase of the flask of each cut-off element is inclined or slightly convexwith respect to the direction of insertion.
 8. The device for cut-off ofa concrete part according to claim 1, wherein insertion of each cut-offelement can be performed individually, after the concrete is cast, thelateral casing of each cut-off element having a tapered shape.
 9. Thedevice for cut-off of a concrete part according to claim 8, whereininsertion of each cut-off element is grouped by a positioning frame, thepositioning frame is fixed before the concrete is cast to salientreinforcing bars by means of spacers spaced angularly between thedifferent tubes of the cut-off elements and resting on a hoop securedlyaffixed to the reinforcing bars.
 10. The device for cut-off of aconcrete part according to claim 9, wherein the spacers extend radiallytowards the inside of the positioning frame to confine an orifice foraxial passage of the concrete casting pipe.
 11. The device for cut-offof a concrete part according to claim 1, wherein the flask is filledwith a delayed-action reactive agent and is placed in position before orafter the concrete is cast.
 12. The device for cut-off of a concretepart according to claim 1, wherein insertion of each cut-off element canbe performed individually, before the concrete is cast, the lateralcasing of each cut-off element having a tapered shape.
 13. The devicefor cut-off of a concrete part according to claim 1, wherein insertionof each cut-off element can be performed in groups by means of apositioning frame, before the concrete is cast, the lateral casing ofeach cut-off element having a tapered shape.
 14. The device for cut-offof a concrete part according to claim 1, wherein insertion of eachcut-off element can be performed in groups by means of a positioningframe, after the concrete is cast, the lateral casing of each cut-offelement having a tapered shape.